The B&H 300 series overhead projectors were first introduced to the market in 1971 with the appearance of the Model 301. This projector featured a cast metal stage frame, cast metal head and arm assembly and a DYS/DYV lamp with a coated glass reflector under the lamp. The unit had a cover actuated AC power interlock assembly. The Model 360 featured a folding mirror and 3 element wide angle lens. Some of the 300 series were equipped with a lamp changer. All of the 300 series overheads used a 14" focal length fresnel and head lenses. The posts on these overheads were mounted with two screws to a metal stud for easy removal until that was replaced by a bottom post mounted bracket. The stage frame was locked to the case by a latch assembly consisting of a fixed bracket and a movable "L" shaped piece held in position by a spring. The "L" shaped bracket was actuated or opened by pressing through the hole onto the "L" bracket with a pencil.

The latch was replaced when the case actuated interlock was removed and replaced with a fixed bracket and stud locked to the base by a sliding mechanism which blocked the operation of the "rocker type" power switch when the cover was unlatched. The 300 series was replaced with the 3800 series by EIKI in 1991, 5 years after they purchased the Audio Visual division from B&H. There is a high degree of parts compatibility between the 300 and 3800 series projectors.

HEAD ASSEMBLY - B&H originally cast the head assemblies but when the lens elements was no longer available from the optics manufacturer and a different diameter lens was used the cast assembly was replaced with a sheet metal version designed to accommodate the new diameter head lenses. The mirror inside the head is the same part in both the cast and the sheet metal versions. The sheet metal head can directly replace the cast head on the existing arm (p/n 079702 per 3800 series manual.)

The original wide angle folding mirror head & coffin shaped mirror and was replaced by a simpler design folding mirror head (p/n 077463) starting with the Model 301L in 1979. This new design head is also used on the 3800 series and mounts on the same arm. There are no parts available for the original head but it can be replaced with the new version.

LAMP HOUSES - There were two lamp houses used in all the 300 series production, a single lamp house and the lamp changer lamp house. Both of these units used the same coated glass reflector that was later replaced by a polished aluminum reflector (p/n 013222.) A thermal fuse was used to protect the projector (and fresnel lens) from overheat if the air flow was restricted or the fan failed. Most models of the 300 series projector contained a "let run" fan thermostat (p/n 42310) which either turned on the fan when the machine reached 142 degrees F or until the projector cooled down below 130 degrees F.

The dual lamp units would allow for lamp swap during a presentation if the main lamp failed. A switch mounted under the lamp house platform swapped power to the lamp socket when the change was made and often blew the lamp because the power hit the lamp while the filament was still quivering having been slammed to the operate position by a panicked presenter. With these older dual lamp machines the safest way to keep from destroying a lamp during changeover is to only have one lamp in position and replace as needed.

One interlock approach was tried with the model 301K which placed a switch under the lamp change lever to interrupt the power during the change cycle. It was not until the 3800 series that the lamp change was interlocked to the main power switch forcing the presenter to turn off the main power before cycling the lamp.

POWER SWITCH, MAIN - The original 301 had a two position single pole power switch (p/n 42309) which looked like a bat less wall light switch, vertically mounted and was covered with a fish paper enclosure. The fan on/off was totally controlled by the thermal switch. The switch, starting with model 301F (1973) was replaced with a 3 position horizontally mounted rocker (p/n 42455) at the time the cover latch was changed to the "hook" and the separate interlock switch was eliminated. The switch became a two position horizontal mounted rocker (p/n 709124) with the model 301K (1978) .

FAN & BRACKET ASSEMBLY - The 301 fan assembly consists of a 3,400 rpm CCW 2 pole motor riveted to an aluminum bracket with an aluminum heat shield protecting the bearings and winding of the motor from the radiant energy of the lamp. Different versions of the lamp houses allowed more or less radiant energy directed to the back side of the fan motor cooking the lubrication from the bearings and adding heat to the windings. Not all of the fan assemblies are equipped with the integral heat shield.

On later production (namely the 3800 series) the heat shield consisted of a bent aluminum bracket mounted to the fan bracket on one of its mount studs (p/n 716176). This folded bracket is NOT present on all versions of the 3800 but is recommended as an add on. There were 5 different part numbers used for the fan and bracket assembly with the differences being the wire lead length and the terminals on the end of the wires and if the motor was mounted on the front or back of the bracket assembly. To solve this problem the present replacement for all of the fan and bracket assemblies have the motor mounted to the bracket and heat shield with 6-32 bolts and nuts and the wire length at the maximum required so the servicer can arrange to match the original configuration as needed.